The Switch
by A Sirius Crush On Moony
Summary: Regulus is in love with his brother, Sirius, who is dating Remus Lupin. Regulus comes up with a plan to switch bodies with Remus, and luckily for him, the switch occurs at a very good moment. RATED M, slash, incest, smut


**I don't write smut very often, so please forgive me if it's terrible. This kinda just popped into my head (yeah, I know. I'm a terrible person, huh).**

 **Warning: RATED M for smut (sex), swearing, incest and well... I suppose rape?**

* * *

 **The Switch**

Regulus Black was a genius. Well, that was what he had decided he was. His best friend, Barty Crouch liked to call him an 'evil, creepy genius'. Regulus tended to drop the 'evil' and 'creepy' part.

"Creepy?" Regulus asked, raising his eyebrows.

"Yes, creepy," Barty replied, looking disturbed. "He is your _brother_."

"So?"

"And you're in love with him," Barty said.

"So?"

"It's creepy!"

"If you say so," Regulus said. "You can't help who you fall in love with."

"It's even creepier that you've cooked up this evil plan," Barty said.

"It's not an evil plan," Regulus said, rolling his eyes. "It's a potion."

"An evil one!"

Regulus sighed. "What's so evil about it?"

"Well, it'll make you and Sirius's boyfriend switch bodies," Barty said.

"Yeah, I know. It was my genius idea, duh."

"It's evil to Lupin," Barty said. "And it's evil to Sirius. He won't even know it's you and Merlin doesn't even want to know what you'll do with him when you're in his boyfriend's body."

"Oh, I have some ideas," Regulus grinned.

"Ew."

"Oh, lighten up. Your only part in this is to keep him occupied when we swap bodies so he doesn't do anything that'll ruin my hour."

"You know I don't agree with this," Barty said.

"I know, but you're my best mate so just do your part, please?" Regulus said. "I know it's bad, but I want Sirius and he'll never want me as me."

"Fine, fine," Barty said. "But it's your funeral when they realise what's happened."

Regulus shrugged and picked up the potion. "Wish me luck!"

"Good luck."

Regulus lifted the potion up to his lips and then drank the whole lot in one gulp.

Everything went dark.

* * *

Regulus opened his eyes and he was no longer sitting in his dormitory. He was in a room which he did not recognise. It was dully lit with candles that smelled of spices and aromas that were somehow extremely arousing. The room was bathed in red; red walls, red carpet, red bed sheets.

The bed took up the entire room. It was a sturdy, wooden four-poster bed draped with silk red curtains that were half closed.

Regulus turned his attention to himself. His potion had worked, obviously. He looked down at his naked body, which was definitely not his body. His skin was not his usual pale flawless skin. No, it was darker, more rugged. He had scars.

His chest hair wasn't as dark as usual. He was more muscular than usual. His legs were longer. His cock was bigger.

Regulus liked being in Remus Lupin's body. He bit down lightly on his bottom lip when he felt a hand graze his erection. The hand wrapped around his cock firmly and began rubbing it up and down slowly, making a tingling sensation wash all over him.

It was then he realised that he was not leaning back against the pillows of the bed. He turned his head and noticed that his naked body was pressed against someone else's naked body.

Sirius. Perfect. He couldn't have picked a better time to switch bodies.

It felt as though a fire had ignited all over when he realised that Sirius was holding his cock. It was Sirius's body wrapped around him. The hard thing digging into his lower back wasn't the wood of the bed, but it was Sirius's erection.

Sirius's hand released Regulus's dick and moved up his abdomen and over his torso. His touch left an invisible trail of electricity that seemed to pulse through every inch of Regulus's body. He had never felt so aroused in his life. Sirius's hands were all over him, and then they were moving slowly down towards his twitching cock which was begging to be touched once more.

Regulus let out a gasp at the touch and let his head fall back against Sirius's shoulder. He groaned quietly when Sirius's lips made contact with his neck. He began kissing and sucking on the soft nape of his neck, sending quiver upon quiver down his entire body.

Regulus couldn't stop himself from turning his head slightly and pressing his lips to Sirius's. It was like a dream come true. He'd wanted this for so long now, and it was much better then he'd expected. Sirius's lips were so soft and gentle on his own, but yet so rough and dominating.

He felt a tongue slip into his mouth and welcomed it hungrily, kissing Sirius back with desperation. He wanted Sirius.

Sirius pulled his mouth away and smiled teasingly at him. Regulus glanced down and let out a low moan as Sirius's hand started pumping his cock faster and firmer.

"You like that, don't you?" Sirius murmured in his ear.

"Mmhm," Regulus replied, trying not to say too much. Sirius couldn't find out it was him.

The feeling that was building up inside him was too much. He couldn't finish yet; it was too quick. He wanted Sirius to fuck him. He wanted to feel Sirius's dick inside him before he was finished here.

He shifted his position. Turning around, he removed Sirius's hand from his cock and pushed him back against the pillows of the bed. Kneeling over him, he traced his fingers across Sirius's chest and let out a slow breath.

His brother was hot. Too hot for his own good. Regulus could just stare down at him all day but he knew he was working on a time limit.

He put one knee on either side of Sirius's body and shifted forwards so that his erection was right in front of Sirius's face.

Sirius stared hungrily at his cock and then up at his face.

"Suck it," Regulus ordered, in a hoarse voice that was not his own. He gasped at the feeling of Sirius's warm, wet mouth surrounding him.

Glancing down, he placed his hands in Sirius's hair and tugged lightly. Sirius looked up at him with a look that was so wanton, it drove him crazy. He took the length of Regulus's cock in his mouth till his nose was buried in the hairs at the base, all the while staring up at him.

Regulus thought he could come right there and then. To have his brother stare up at him with that look, while sucking him off was the sexiest thing he could possibly think of.

"Yes," he breathed, tugging at Sirius's hair and pulling him back.

Sirius caught his breath for a second and then he was down again, sucking up and down the length of Regulus's dick.

Sirius expertly swirled his tongue round the head in a swift, circular motion, keeping his entire mouth closed around the shaft.

 _How the fuck is he so good at this?_

Regulus thrust into Sirius's mouth hard, holding his head in place. He looked down at Sirius's face. His eyes began watering, but he stared up at Regulus and gave him a look that was so teasing that Regulus couldn't help but thrust again, and again and again.

He shoved his cock so far back down Sirius's throat that he could feel his brother's struggle and then he pulled out quickly and smirked down at him.

"Why are you being so bad today?" Sirius panted.

"Because I want you so bad," Regulus whispered, reaching behind him and grabbing Sirius's hard cock and placing it in between his cheeks so it touched his ass hole. He felt a responsive thrust from Sirius.

 _Oh fuck yes._

Sirius grabbed his own cock and pulled it away from Regulus's ass, and then let go of it so it snapped back, slapping against him hard.

"Mmm."

Sirius pushed Regulus off of him and got off the bed. He stood up and held his dick out.

"Your turn," Sirius mumbled.

Regulus practically jumped off the bed and got down on his knees. He reached for Sirius's cock and placed it in his mouth.

He began sucking up and down, and up and down, and then pulled back to catch his breath.

 _Fuck, this is harder than I thought. Damn him for having a massive-OH!_

Before he knew what was happening, Sirius was thrusting deep into his mouth and he could do nothing but take it. His jaw ached and he was terrified he was going to gag, but he loved every second of it.

"Take it deep – _yes_ … fuck."

Regulus felt it hit the back of his throat and he pulled back before he could gag. He stared up at Sirius and wiped his mouth with the back of his hand.

"Not feeling it today?" Sirius asked, looking amused.

Obviously Lupin was good at giving head, which evidently, Regulus was not too good at. He tried not to let it bother him – it was his first time after all.

Regulus stood up and leaned close to Sirius. "No, I'm just desperate for you to fuck me."

"Oh," Sirius replied, biting his lip and smirking at him. "Eager, are we?"

"Yes," Regulus whispered. "I just want you to fill me up completely and fuck me like there's no tomorrow."

"What's gotten into you?" Sirius moaned. "I love it. You're _so_ bad."

Regulus smiled and led Sirius back onto the bed. Taking control, Sirius grabbed him and pushed him against the pillows. Regulus loved the thought of Sirius pushing him around and using him.

Sirius pushed Regulus's legs wide apart. "Touch yourself," he said.

Regulus did as his was told, reaching down and stroking himself while he watched Sirius watch him with lust-filled eyes. Then, Sirius lowered himself down, and Regulus was surprised when he felt a tongue graze his ass hole.

"Ah- _yes_ …"

He felt Sirius's tongue slide back and forth over the hole, and then round and round, sending shivers up and down his spine and making his cock twitch in his hand.

Regulus was on the brink of exploding. The thought that turned him on the most was that Sirius had no idea that it was Regulus he was about to fuck.

 _He's going to fuck his little brother and he doesn't even know it._

The thought made him moan loudly, and Sirius glanced up at him while keeping his tongue moving. Then, Sirius's tongue was gone. Regulus looked down to see Sirius sucking on his fingers, and then the fingers were touching him.

Slowly, Sirius pushed one finger inside him, stretching him open. Regulus braced himself for the pain, but none came. He let out a breath, and then Sirius inserted another finger, and then another. He kept his fingers still for about a minute and then started moving them in deeper.

 _SHIT, THAT'S GOOD._

He pulled his fingers out completely and knelt up. Grabbing his cock, Sirius placed it in line with Regulus's stretched hole and then slowly pressed into him.

It was surprisingly painless for his first time, but then he realised it must be because he was in a body that was used to being stretched open.

Still, the pain came, and Regulus gritted his teeth as Sirius's cock slowly filled him up. Sirius stopped, waiting for him to adjust to the intrusion.

Regulus nodded, when it became comfortable and Sirius pushed further into him, until his entire length was inside.

Regulus tried to breathe evenly. Sirius grabbed each of Regulus's legs, keeping them apart and then slowly pulled back almost all the way and then pushed gently in once more. Regulus's whole body felt like it was on fire. He stared up longingly at Sirius as he fucked him and let out a groan.

"Fuck, Sirius," he said, reaching down and stroking his cock. "Faster - harder – please."

"If you insist," Sirius said, increasing the speed almost instantly. The whole bed was shaking and creaking loudly as Sirius slammed into him with all the force he had.

Sirius leaned forwards, letting go of Regulus's legs, and began kissing him sloppily on the lips, while keeping his rhythm going.

Regulus tried to kiss back but his mind was too preoccupied with Sirius's dick inside him, hitting his spot. Every. Damned. Time.

 _Oh Merlin, that's too good._

Sirius pulled back again and then pulled out completely. The sudden emptiness was a strange feeling. He _needed_ Sirius back inside him. His ass was aching for it.

Sirius rolled over, and lay flat on his back, his cock flush against his stomach. It was rock solid and dripping with sticky precum.

"Sit on it," Sirius said.

Regulus scrambled to get on top, placing his legs on either side of Sirius's hips and positioning himself over his cock. Sirius reached down and held his erection in place for Regulus to sit on.

Slowly, Regulus lowered himself down. He felt it slip inside easily. He lowered himself down more until it was completely inside him.

Regulus lifted himself up a little and then before he could sit back down on it, Sirius held him frozen in place.

"Let me," Sirius murmered seductively, and Regulus thought his legs would buckle beneath him when Sirius began slamming up into him fast and hard.

"Fuck, Sirius," he panted, as he threw his head back. Sirius pounded him harder and harder and grabbed Regulus's hand and forced him to stroke himself.

Regulus pumped his cock faster and faster in time with Sirius's thrusts and he could feel the orgasm rising in him. He was going to come soon, and he wanted to come in Sirius's mouth.

He kept stroking himself, waiting for the right moment. When he knew he was finished, he climbed off of Sirius's cock and shuffled over to his face.

Sirius stared up at him in surprise and opened his mouth expectantly. Regulus felt his release he spilled his load all over Sirius's face. He watched Sirius's expression as he swallowed the cum that had been shot into his mouth, and then proceeded to lick his lips.

"Get down there, right now," Sirius growled, pushing Regulus down so that his head was in line with Sirius's cock.

Sirius began pumping his cock right in front of Regulus's face and the mere sight made Regulus's dick twitch again.

He could hear Sirius's breathing become louder, and his strokes were getting faster and faster.

Regulus leaned forwards a bit, and then Sirius's cum was all over his face. He took Sirius's cum-covered cock in his mouth and sucked it dry, swallowing every last drop.

It was so hot and sweet, and tastier than he'd expected. He pulled Sirius's dick out of his mouth, he slapped it against his cheek, smearing the cum all over.

Sirius grabbed him and pulled him up so that they were lying next to each other. "That was fucking incredible," Sirius said.

"I know," Regulus replied.

"No honestly," Sirius growled. "Best night of my life. It's never been that good before. Whatever's gotten into you, I love it."

Regulus smirked. If only he knew…

"You've got cum on your face, by the way," Sirius teased.

"I wonder why that is?" Regulus replied.

Sirius rolled his eyes and reached over. He had his wand in his hand. He muttered " _scougify_ " and they were both cleaned.

"Let's sleep," Sirius said.

"Okay," Regulus mumbled, realising how tired he actually was.

Sirius wrapped his arms around him and pulled him close. He planted a kiss on Regulus's forehead.

"G'night," Sirius whispered. "I love you."

Regulus knew the words weren't meant for him, but he couldn't help but say "I love you, too."

He let his eyes fall closed as he drifted off to sleep.

* * *

Regulus awoke seconds later and he was no longer lying in Sirius's arms. He was back in his dormitory.

"Aw," he said, feeling disappointed. It was over.

He glanced up at Barty, who looked confused.

"Are you back?"

"Yeah, sadly," Regulus said.

"Thank Merlin, that guy was a right idiot," Barty said. "Sorry about the injury, by the way."

"Injury?"

"I punched him in the face when he tried to escape," Barty said. "Apparently it was quite painful."

Regulus sniggered. "I can understand why he was annoyed. I did take him away from a pretty amazing moment."

"My ears do not need to hear this," Barty replied. "Please save me the torture."

"Does he know we swapped bodies? Did he see himself in a mirror or anything?"

"Yep," Barty said. "I told you, it's your funeral."

"Damn it," Regulus said.

* * *

Regulus was walking down the corridor towards the Great Hall for dinner, when he saw Sirius marching towards him, looking annoyed.

He felt his cheeks redden as he realised Sirius probably knew what had happened.

"Reg. Oi, don't walk away from me!" Sirius yelled.

Regulus turned around and acted surprised. "Oh, hey! Sorry, Sirius. I didn't recognise you with clothes."

"I-huh?"

"Yeah."

"I don't know what you mean, but what did you do to Remus?"

"I did nothing to Lupin, but check out what he did to me," Regulus said, pointing at his bruised face. "Hurts like hell."

"Shut up," Sirius said. "He told me you did something and he won't tell me what because he says I probably don't want to know."

"Oh, so you don't know?" Regulus asked, smirking a little.

"Why are you looking at me like that?" Sirius asked.

"Oh, nothing," Regulus shrugged. "Just, I didn't do anything to Lupin. I did something to you though."

"What the heck are you on about?"

"Well," Regulus said, deciding it would be more amusing to tell Sirius the story than it would be embarrassing. "Your boyfriend and I switched bodies."

" _Huh_?"

"Yup. My fault, actually. I thought it would be fun," Regulus said. "It was more fun than I'd anticipated."

"When did this happen?" Sirius demanded.

"Well let's just say, I gave you the best night of your life," Regulus smirked.

He watched in amusement as Sirius realised what he meant. Sirius's mouth dropped open and for the first time ever, he was lost for words. He stared blankly at Regulus and then, finally closed his mouth and swallowed hard.

"I-no-you're lying!"

"I'm not," Regulus said, leaning closer to him. "By the way, I love that thing you do with your tongue."

Sirius's eyes widened in horror. "Oh Merlin."

"Well, just so you know, it was the best night of my life, too," Regulus said.

"Why would you even… ugh… Reg, why would you _do_ that?"

Now it was time for Regulus to feel embarrassed. "Well, don't freak out."

"I think I'm already freaking out," Sirius said.

"I'm kind of in love with you."

"I'm your brother," Sirius exclaimed. "You let me do that-fuck."

"I know you're my brother, and I'm selfish," Regulus said. "I know that, and I know that what I did was wrong. I just knew that you would never ever want to be with me, so I did something I shouldn't have so I could have you for one moment in my life. You can go back to fucking him now, it's okay."

Sirius blinked at him in disbelief.

"I can't believe this…"

"I'm sorry. I'll go now."

"I kept going on about it to him after," Sirius said. "About how it was better than ever before. I didn't understand why he was so angry about that."

"Sorry."

"He broke up with me," Sirius carried on. "That's why I came to talk to you. He said he broke up with me because you did something to him."

"Oh," Regulus said, feeling guilty.

"I'd like to get him back, but while I'm single," Sirius said, stepping closer. "Why don't we just, you know… have a little bit of fun?"

Regulus's face lit up. "Really?"

"Well," Sirius said, blushing and looking down at his feet. "I know it's bad and we shouldn't, but something about how bad it is makes me want to do it more. And I know you're good at it."

"Am I now?"

"Yeah, apart from the blowjob," Sirius said. "You're not so good at that."

"Hey!"

"It's okay," Sirius said. "Let's go. I'm hungry and I've been craving some cock."

"Oh… okay," Regulus said, blushing. "But just so you know, mine isn't as big as-"

"-Shh," Sirius said. "I don't care. Come on."

Regulus bit his lip and followed Sirius. He couldn't believe it.

Maybe he was a genius after all.

 **~The End~**


End file.
